The use of metallic tapes has become useful in the detection of underground plastic pipe and utility lines. Also, ceramic and other nonmetallic materials such as concrete are used in underground service. The precise location of nonmetallic lines cannot be determined by metal detectors so that a simple method was devised to lay a metallic foil and polymer tape over the line which could be detected in the usual manner. Plastic tapes also have become quite useful in marking areas above ground. The tapes are strung around hazardous areas, police investigation lines and can generally serve as demarcation for any purpose. The tapes used for above ground marking are not reinforced and can be easily torn.
This invention is a reinforced metallic tape that has superior tensile strength that has benefits for use in detection of underground utility as well as above ground demarcation tapes. The high tensile strength is particularly beneficial in the layout operation for underground line marking. The metallic layer also has reflective qualities for use as an above ground marking tape. The tape can have pressure sensitive adhesive so that it can be applied to posts and barriers for marking purposes. The reinforced tapes can be colored and prepared with or without a printed message.
U.S. Pat. No. 3,633,533 discloses a method to locate underground service lines using a metal film coated with a colored plastic. The tape ia not reinforced and has certain drawbacks remedied by the present invention. When a trench is dug for a utility line and a detectable tape is used, typically, the line is laid first. Then there is a partial backfilling of the trench and the tape is laid over the line coming off a roll on a tractor. Then in a continuous process the trench backfilling is completed. As the tape is laid there may be some tension placed on it, as the backfill process is completed, stretching the tape. During this process if too much tension is placed on the tape, it can break causing the operation to be halted until the tape can be mended. Also, the foil layer is not elastic and tension on the tape may cause the metallic foil to break while the plastic coatings are stretched. In some cases a continuous length of metallic conductive material is desirable. Also, the present plastic coated types have a tendency to curl on the edges and care must be taken when laying the tape that it does not become twisted or folded. Although the plastic coated metallic foil tapes have provided a cost efficient method to detect underground piping systems, there are some aspects which can be improved upon.
The present invention is an improved detectable tape which is reinforced. The reinforcing material imparts tensile strength to the tape such that the tape and the foil layer are protected from tearing during the trench backfilling process and the use above ground for marking purposes. For underground usage the metallic foil layer is covered with a thermoplastic layer on the side which is not laminated to the reinforcing material. The metallic layer should be protected from environmental degradation and oxidation. This embodiment may also be used above ground.
Another property is that the reinforced tape does not have a tendency to curl at the edges or twist. The tape lies flat as it comes off a roll. These properties are beneficial from the installation viewpoint, because as the reinforced tape comes off the roll into the trench, there is less likelihood to tear because of the high tensile strength and the tendency of the tape not to curl will make it easier to lay the tape out in the trench.
The reinforced tape can be printed with cautionary messages. Also, a color coating resin can laminate the foil layer and the reinforcing material. This gives a foil or metallic layer on one side and a colored layer on the other. With a nonwoven essentially clear resin reinforcing layer the color coating is clearly visible through the reinforcing layer. Certain color codes have been preselected for use with certain utility installations which can be used in this invention.
The present invention is illustrated by the embodiments in the accompanying drawings.